Photoelectric conversion device, imaging system, and movable body

ABSTRACT

A photoelectric conversion device includes a pixel isolation portion and a concavo-convex structure. The pixel isolation portion is arranged between adjacent pixels in a plurality of pixels formed in a semiconductor layer. The concavo-convex structure is formed on a light receiving surface of the semiconductor layer. The concavo-convex structure includes a trench extending toward an oblique direction from the light receiving surface to an inside of the semiconductor layer. The trench is filled with material that is different from material of the semiconductor layer positioned around the trench.

BACKGROUND Field

The present disclosure relates to a photoelectric conversion device, animaging system, and a movable body.

Description of the Related Art

Japanese Patent Application Laid-Open No. 2021-061330 discloses aphotoelectric conversion device in which quantum efficiency is improvedby providing a concavo-convex structure on the light receiving surfaceof the photoelectric conversion device.

However, the concavo-convex structure disclosed in Japanese PatentApplication Laid-Open No. 2021-061330 may not be always sufficient interms of sensitivity to incident light.

The present disclosure is made to provide a photoelectric conversiondevice, an imaging system, and a movable body that can further increasesensitivity.

SUMMARY

A photoelectric conversion device according to one aspect of the presentdisclosure includes a pixel isolation portion and a concavo-convexstructure. The pixel isolation portion is arranged between adjacentpixels of a plurality of pixels formed on a semiconductor layer. Theconcavo-convex structure is formed on a light receiving surface of thesemiconductor layer. The concavo-convex structure includes a trenchextending toward an oblique direction from the light receiving surfaceto an inside of the semiconductor layer. The trench is filled withmaterial that is different from material of the semiconductor layerpositioned around the trench.

Further features of the present disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a photoelectric conversion deviceaccording to the first embodiment.

FIG. 2 is a diagram illustrating an arrangement example of a sensorsubstrate in the first embodiment.

FIG. 3 is a diagram illustrating an arrangement example of a circuitsubstrate according to the first embodiment.

FIG. 4 is a circuit diagram of an APD and a pulse generator according tothe first embodiment.

FIG. 5A is a diagram illustrating the relationship between the operationof the APD and an output signal in the first embodiment.

FIG. 5B is a diagram illustrating the relationship between the operationof the APD and an output signal in the first embodiment.

FIG. 5C is a diagram illustrating the relationship between the operationof the APD and an output signal in the first embodiment.

FIG. 6 is a cross-sectional view of a plurality of adjacent pixels inthe first embodiment.

FIG. 7 is a cross-sectional view of the concavo-convex structureaccording to the first embodiment.

FIG. 8A is a plan view of the concavo-convex structure according to thefirst embodiment on the line A-A′.

FIG. 8B is a plan view of the concavo-convex structure according to thefirst embodiment on the line B-B′.

FIG. 8C is a plan view of the concavo-convex structure according to thefirst embodiment on the line C-C′.

FIG. 9A is a cross-sectional view of the concavo-convex structureaccording to the first embodiment.

FIG. 9B is a cross-sectional view of the concavo-convex structureaccording to the first embodiment.

FIG. 10 is a cross-sectional view of the concavo-convex structureaccording to the second embodiment.

FIG. 11 is a cross-sectional view of the concavo-convex structureaccording to the third embodiment.

FIG. 12A is a plan view of the concavo-convex structure according to thethird embodiment on the line A-A′.

FIG. 12B is a plan view of the concavo-convex structure according to thethird embodiment on the line B-B′.

FIG. 12C is a plan view of the concavo-convex structure according to thethird embodiment on the line C-C′.

FIG. 13 is a cross-sectional view of the concavo-convex structureaccording to the fourth embodiment.

FIG. 14A is a plan view of the concavo-convex structure according to thefourth embodiment on the line A-A′.

FIG. 14B is a plan view of the concavo-convex structure according to thefourth embodiment on the line B-B′.

FIG. 14C is a plan view of the concavo-convex structure according to thefourth embodiment on the line C-C′.

FIG. 15 is a cross-sectional view of the concavo-convex structureaccording to the fifth embodiment.

FIG. 16A is a plan view of the concavo-convex structure according to thefifth embodiment on the line A-A′.

FIG. 16B is a plan view of the concavo-convex structure according to thefifth embodiment on the line B-B′.

FIG. 16C is a plan view of the concavo-convex structure according to thefifth embodiment on the line C-C′.

FIG. 17 is a cross-sectional view of the concavo-convex structureaccording to the sixth embodiment.

FIG. 18A is a plan view of the concavo-convex structure according to thesixth embodiment on the line A-A′.

FIG. 18B is a plan view of the concavo-convex structure according to thesixth embodiment on the line B-B′.

FIG. 18C is a plan view of the concavo-convex structure according to thesixth embodiment on the line C-C′.

FIG. 19A is a plan view of the concavo-convex structure according to theseventh embodiment.

FIG. 19B is a plan view of the concavo-convex structure according to theseventh embodiment.

FIG. 19C is a plan view of the concavo-convex structure according to theseventh embodiment.

FIG. 20 is a cross-sectional view of the concavo-convex structureaccording to the eighth embodiment.

FIG. 21A is a plan view of the concavo-convex structure according to theeighth embodiment on the line A-A′.

FIG. 21B is a plan view of the concavo-convex structure according to theeighth embodiment on the line B-B′.

FIG. 21C is a plan view of the concavo-convex structure according to theeighth embodiment on the line C-C′.

FIG. 22A is a plan view of the concavo-convex structure according to theeighth embodiment.

FIG. 22B is a plan view of the concavo-convex structure according to theeighth embodiment.

FIG. 23 is a cross-sectional view of the photoelectric conversionapparatus according to the ninth embodiment.

FIG. 24 is a cross-sectional view of the concavo-convex structureaccording to the tenth embodiment.

FIG. 25 is a cross-sectional view of the concavo-convex structureaccording to the eleventh embodiment.

FIG. 26 is a cross-sectional view of the concavo-convex structureaccording to the eleventh embodiment.

FIG. 27 is a cross-sectional view of a plurality of adjacent pixelsaccording to the twelfth embodiment.

FIG. 28 is a block diagram of a photodetection system according to thethirteenth embodiment.

FIG. 29 is a block diagram of a photodetection system according to thefourteenth embodiment.

FIG. 30 is a schematic diagram of an endoscope surgery system accordingto the fifteenth embodiment.

FIG. 31 is a schematic diagram of a light detection system according tothe sixteenth embodiment.

FIG. 32A is a schematic diagram of a movable body according to thesixteenth embodiment.

FIG. 32B is a schematic diagram of a movable body according to thesixteenth embodiment.

FIG. 32C is a schematic diagram of a movable body according to thesixteenth embodiment.

FIG. 33 is a flowchart illustrating an operation of the light detectionsystem according to the sixteenth embodiment.

FIG. 34A is a diagram illustrating a specific example of an electronicdevice according to the seventeenth embodiment.

FIG. 34B is a diagram illustrating a specific example of an electronicdevice according to the seventeenth embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will be described below withreference to the accompanying drawings. The following embodiments areintended to embody the technical idea of the present disclosure and donot limit the present disclosure. The sizes and positional relationshipsof the members shown in the drawings may be exaggerated for clarity ofexplanation. In the following description, the same components aredenoted by the same reference numerals, and description thereof may beomitted.

In the following description, terms indicating a specific direction orposition (for example, “top”, “bottom”, “right”, “left”, and other termsincluding those terms) are used as necessary. The use of those terms isto facilitate understanding of the embodiments with reference to thedrawings, and the technical scope of the present disclosure is notlimited by the meaning of those terms.

First Embodiment

The configuration of the photoelectric conversion device according tothe present embodiment will be described with reference to FIGS. 1 to 4. The photoelectric conversion device includes SPAD pixels eachincluding an avalanche photodiode (hereinafter referred to as “APD”). Ofcharge pairs generated in the APD, a conductivity type of charge used asa signal charge is referred to as a first conductivity type. The firstconductivity type refers to a conductivity type in which a charge havingthe same polarity as the signal charge is used as a majority carrier.Further, a conductivity type opposite to the first conductivity type isreferred to as a second conductivity type. The following explanationdescribes an example in which the signal charges are electrons, thefirst conductivity type is N-type, and the second conductivity type isP-type. However, the signal charges may be holes, the first conductivitytype may be P-type, and the second conductivity type may be N-type. Inthis specification, the term “plan view” refers to a view from adirection perpendicular to a light incident surface of a semiconductorsubstrate described later. The “cross section” refers to a surface in adirection perpendicular to the light incident surface of the sensorsubstrate 1. When the light incident surface of the semiconductor layeris a rough surface when viewed microscopically, a planar view is definedwith reference to the light incident surface of the semiconductor layerwhen viewed macroscopically. The “depth direction” is a direction fromthe light incident surface (first surface) of the sensor substrate 1toward the surface (second surface) on which the circuit substrate 2 isarranged.

FIG. 1 is a schematic diagram of a photoelectric conversion deviceaccording to the present embodiment, and shows a configuration of astacked photoelectric conversion device 100. The photoelectricconversion device 100 includes a sensor substrate (first substrate) 1and a circuit substrate (second substrate) 2 stacked on each other, andthe sensor substrate 1 and the circuit substrate 2 are electricallyconnected to each other. The photoelectric conversion device accordingto the present embodiment is a back-illuminated photoelectric conversiondevice in which light is incident from a first surface of the sensorsubstrate 1 and the circuit substrate 2 is arranged on a second surfaceof the sensor substrate 1. The sensor substrate 1 includes a firstsemiconductor layer having photoelectric conversion elements describedlater and a first wiring structure. The circuit substrate 2 includes asecond semiconductor layer having a circuit such as a signal processingunit described later and a second wiring structure. The photoelectricconversion device 100 is formed by stacking the second semiconductorlayer, the second wiring structure, the first wiring structure, and thefirst semiconductor layer in this order.

Hereinafter, the sensor substrate 1 and the circuit substrate 2 may bediced chips, but are not limited to chips. For example, each substratemay be a wafer. Further, each substrate may be diced after beinglaminated in a wafer state, or chips may be stacked and bonded afterbeing formed into chips. The sensor substrate 1 is provided with a pixelregion 1 a, and the circuit substrate 2 is provided with a circuitregion 2 a for processing a signal detected by the pixel region 1 a.

FIG. 2 is a diagram illustrating an arrangement example of the sensorsubstrate 1. The plurality of pixels 10 each include an APD 11, and arearranged in a two-dimensional array in a plan view to form a pixelregion 1 a.

The pixel 10 is typically a pixel for forming an image, but when it isused in a TOF (Time of Flight), the pixel 10 does not necessarily needto form an image. That is, the pixel 10 may be a pixel for measuring thetime at which light reaches and the amount of light.

FIG. 3 is a diagram illustrating an arrangement example of the circuitsubstrate 2. The circuit substrate 2 includes a signal processing unitor circuit 20, a vertical scanning circuit 21, a readout circuit 23, ahorizontal scanning circuit 27, an output calculation unit or circuit24, a control pulse generation circuit 25, a scanning line 26, and asignal line 29. The circuit region 2 a is arranged in a regionoverlapping the pixel region 1 a in FIG. 2 in a plan view. Further, inthe plan view in FIG. 2 , the vertical scanning circuit 21, the readoutcircuit 23, the horizontal scanning circuit 27, the output calculationunit 24, and the control pulse generation circuit 25 are disposed tooverlap with a region between the edge of the sensor substrate 1 and theedge of the pixel region 1 a. That is, the sensor substrate 1 has apixel region 1 a and a non-pixel region arranged around the pixel region1 a, and the vertical scanning circuit 21, the readout circuit 23, thehorizontal scanning circuit 27, the output calculation unit 24, and thecontrol pulse generation circuit 25 are arranged in a region overlappingthe non-pixel region in a plan view.

The signal processing units 20 are electrically connected to the pixels10 through connection wirings each provided for the pixel 10, and arearranged in a two-dimensional array in a plan view, similarly to thepixels 10. The signal processing unit 20 includes a binary counter thatcounts photons incident on the pixel 10.

The vertical scanning circuit 21 receives a control pulse supplied fromthe control pulse generation circuit 25, and supplies the control pulseto the signal processing unit 20 corresponding to the pixels 10 in eachrow via the scanning line 26. The vertical scanning circuit 21 mayinclude a logic circuit such as a shift register or an address decoder.

The readout circuit 23 acquires a pulse count value of a digital signalfrom the signal processing unit 20 of each row via the signal line 29.Then, an output signal is output to a signal processing circuit (signalprocessing device) outside the photoelectric conversion device 100 viathe output calculation unit 24. The readout circuit 23 may have afunction of a signal processing circuit for correcting the pulse countvalue or the like. The horizontal scanning circuit 27 receives thecontrol pulse from the control pulse generation circuit 25, andsequentially outputs the pulse count value of each column in the readoutcircuit 23 to the output calculation unit 24. As described later, whenthe pulse count value exceeds a threshold value, the output calculationunit 24 estimates an actual image signal (pulse count value) based onthe time count value included in additional information and thethreshold value, and replaces (extrapolates) the pulse count value withthe estimated pulse count value. On the other hand, when the pulse countvalue is equal to or smaller than the threshold value, the pulse countvalue is output as an image signal as it is.

The output calculation unit 24 performs a predetermined process on thepulse count value read by the readout circuit 23, and outputs an imagesignal to the outside. As will be described later, when the pulse countvalue exceeds the threshold value, the output calculation unit 24 canperform processing such as calculation of the pulse count value.

In FIG. 2 , the arrangement of photoelectric conversion elements in thepixel region 1 a may be one-dimensionally arranged. In addition, theeffect of the present disclosure can be achieved even in a configurationin which one pixel is provided, and a configuration in which one pixelis provided can be included in the present disclosure. In thephotoelectric conversion device having a plurality of pixels, the effectof suppressing the circuit scale according to the present embodimentbecomes more significant. It is not necessary to provide one signalprocessing unit 20 for every pixel 10. For example, one signalprocessing unit 20 may be shared by a plurality of pixels 10 and signalprocessing may be sequentially performed.

FIG. 4 is a block diagram of the APD and a pulse generation unitaccording to the present embodiment. FIG. 4 illustrates the pixels 10 ofthe sensor substrate 1 and a pulse generation unit 22 in the signalprocessing unit 20 of the circuit substrate 2. The APD 11 is disposed inthe pixel 10. The pulse generation unit 22 includes a quenching element221, a waveform shaping unit 222, a counter circuit 223, and a selectioncircuit 224.

The APD 11 generates charge pairs corresponding to incident light byphotoelectric conversion. A voltage VL (first voltage) is supplied to ananode of the APD 11. A voltage VH (second voltage) higher than thevoltage VL supplied to the anode is supplied to a cathode of the APD 11.A reverse bias voltage is applied to the anode and the cathode, and theAPD 11 is in a state capable of avalanche multiplication. When photonsenter the APD 11 in a state where the reverse bias voltage is supplied,charges generated by the photons cause avalanche multiplication, and anavalanche current is generated.

The APD 11 can operate in a Geiger mode or a linear mode according tothe voltage of the reverse bias. The Geiger mode is an operation in astate where the potential difference between the anode and the cathodeis higher than the breakdown voltage, and the linear mode is anoperation in a state where the potential difference between the anodeand the cathode is near or lower than a breakdown voltage. An APDoperating in the Geiger mode is particularly referred to as SPAD orSPAD-type. As an example, the voltage VL (first voltage) may be −30 Vand the voltage VH (second voltage) may be 1 V. The APD 11 may operatein a linear mode or a Geiger mode. When the APD 11 operates as the SPAD,the potential difference becomes larger than that of the APD 11 in thelinear mode, and the effect of the withstand voltage becomessignificant. Accordingly, the SPAD is preferable in this case.

The quenching element 221 is provided between the power supply line forsupplying the voltage VH and the cathode of the APD 11. The quenchingelement 221 functions as a load circuit (quenching circuit) at the timeof signal multiplication by avalanche multiplication, and has a functionof suppressing a voltage supplied to the APD 11 and suppressingavalanche multiplication (quenching operation). Further, the quenchingelement 221 has a function of returning the voltage supplied to the APD11 to the voltage VH by flowing a current corresponding to the voltagedrop in the quenching operation (recharging operation).

The waveform shaping unit 222 functions as a signal generation unit thatgenerates a detection pulse based on an output generated by incidence ofa photon. That is, the waveform shaping unit 222 shapes the potentialchange of the cathode of the APD 11 obtained at the time of photondetection, and outputs a rectangular wave pulse signal (detectionpulse). As the waveform shaping unit 222, for example, an invertercircuit is used. Although FIG. 4 shows an example in which one inverteris used as the waveform shaping unit 222, a circuit having a pluralityof inverters are connected in series may be used. Other circuits havinga waveform shaping effect may also be used.

The counter circuit 223 counts the pulse signals output from thewaveform shaping unit 222 and holds the count value. Further, a controlpulse is supplied from the vertical scanning circuit 21 shown in FIG. 3to the counter circuit 223 through a driving line 226 included in thescanning line 26. When the control pulse becomes active, the signal heldin the counter circuit 223 is reset.

The selection circuit 224 includes a switch circuit, a buffer circuitfor outputting a signal, and the like. The selection circuit 224 issupplied with a control pulse from the vertical scanning circuit 21shown in FIG. 3 through a driving line 227. In accordance with thecontrol pulse, the selection circuit 224 electrically switches aconnected state or a non-connected state between the counter circuit 223and a signal line 219.

A switch such as a transistor may be provided between the quenchingelement 221 and the APD 11, and between the APD 11 and the signalprocessing unit 20. Alternatively, the supply of the voltage VH or thevoltage VL may be electrically switched by a switch such as atransistor.

FIGS. 5A, 5B, and 5C are diagrams illustrating the relationship betweenthe operation of the APD and the output signal in the presentembodiment. FIG. 5A is a diagram extracted from the APD 11, thequenching element 221, and the waveform shaping unit 222 in FIG. 4 .When the input side and the output side of the waveform shaping unit 222are node A and node B, FIG. 5B illustrates a waveform change of node Aand FIG. 5C illustrates a waveform change of node B.

In a period from time t0 to time t1, a reverse bias voltage of VH-VL isapplied to the APD 11. When a photon is incident on the APD 11 at thetime t1, avalanche multiplication occurs in the APD 11, an avalanchemultiplication current flows in the quenching element 221, and thevoltage of node A drops. When the voltage drop further increases and thepotential difference applied to the APD 11 decreases, the avalanchemultiplication of the APD 11 stops at time t3, and the voltage level ofthe node A does not drop by a certain constant value or more. Afterthat, in a period from time t3 to time t5, a current that compensates avoltage drop from the voltage VL flows through the node A, and at thetime t5, the node A is settled to the original voltage level. At thistime, from time t2 to time t4, when the voltage level of the node A islower than the threshold value of the waveform shaping unit 222, thenode B becomes high level. That is, the voltage waveform of node A isshaped by the waveform shaping unit 222, and a rectangular wave pulsesignal is output from node B.

The structure of the pixel 10 according to the present embodiment willbe described with reference to FIGS. 6 to 8C. FIG. 6 is across-sectional view of a plurality of adjacent pixels. As shown in FIG.6 , the pixel 10 includes a semiconductor layer 110 and an insulatinglayer 140.

The semiconductor layer 110 includes a plurality of semiconductorregions constituting the APD 11. The semiconductor layer 110 has a firstsurface on which light enters and a second surface which is a surfaceopposite to the first surface. In the present specification, the depthdirection is a direction from the first surface to the second surface ofthe semiconductor layer 110 in which the APD 11 is arranged.Hereinafter, the “first surface” may be referred to as the “backsurface” or the “light receiving surface”, and the “second surface” maybe referred to as the “front surface”. The direction from apredetermined position of the semiconductor layer 110 toward the surfaceof the semiconductor layer 110 may be described as “deep”. The directionfrom a predetermined position of the semiconductor layer 110 toward theback surface of the semiconductor layer 110 may be described as“shallow”.

The semiconductor layer 110 is formed of silicon (Si), indium galliumarsenide (InGaAs), or the like. The semiconductor layer 110 has a firstsemiconductor region 111, a second semiconductor region 112, a thirdsemiconductor region 113, and a fourth semiconductor region 114. Thefirst semiconductor region 111 having the first conductivity type andthe second semiconductor region 112 having the second conductivity typeform a PN junction. The impurity concentration of the firstsemiconductor region 111 is higher than that of the second semiconductorregion 112. A predetermined reverse bias voltage is applied to the firstsemiconductor region 111 and the second semiconductor region 112,thereby forming an avalanche multiplication region of the APD 11.

As shown in FIG. 6 , the third semiconductor region 113 having thesecond conductivity type is arranged on the same layer as the firstsemiconductor region 111. The third semiconductor region 113 is alsoarranged at a position shallower than the second semiconductor region112. The impurity concentration of the third semiconductor region 113 islower than that of the second semiconductor region 112. The thirdsemiconductor region 113 is a region for absorbing light incident fromthe light receiving surface. The fourth semiconductor region 114 havingthe second conductivity type is arranged at a position shallower thanthe third semiconductor region 113. The impurity concentration of thefourth semiconductor region 114 is higher than that of the thirdsemiconductor region 113. A concavo-convex structure 170 including aplurality of trenches 171 described later is formed on the side of thelight receiving surface of the fourth semiconductor region 114. The term“structure” refers to an arrangement of interrelated elements or anintegral element constructed or patterned according to a predeterminedform or shape. It may be an assembly of components or integral element,a pattern, an assembly, a part, a piece, or a segment.

A pixel isolation portion 120 having a structure in which an insulator(dielectric) is embedded in the semiconductor layer 110 is arrangedbetween the pixels 10 adjacent to each other. The term “portion” refersto a part, a section, a segment, a circuit, or a sub-assembly of thesemiconductor layer 110. The pixel isolation portion 120 has a deeptrench isolation (DTI) structure. The pixel isolation portion 120 isformed by etching or the like. The pixel isolation portion 120 is formedfrom the side of the light receiving surface, and shallower than thethickness of the semiconductor layer 110. In the present embodiment, thepixel isolation portion 120 is formed to gradually decrease in widthfrom the light receiving surface side toward the front (second) surfaceside. That is, the pixel isolation portion 120 has a wedge shape. Thepixel isolation portion 120 repeatedly reflects incident light insidethe semiconductor layer 110 to improve the efficiency of photoelectricconversion in the semiconductor layer 110 and the sensitivity of thepixels. By forming the pixel isolation portion 120 in a wedge shape, thelateral reflection efficiency of the semiconductor layer 110 can beenhanced.

The pixel isolation portion 120 may be formed in a columnar shape or ina prismatic shape. The pixel isolation portion 120 may be formed fromthe second (front) surface side, which is a surface facing the lightreceiving surface, or may be formed to penetrate the semiconductor layer110. The pixel isolation portion 120 may be formed to surround theentire one pixel 10 or may be formed to partially surround the one pixel10 in a plan view. The dielectric having a refractive index lower thanthat of a semiconductor element such as silicon oxide can be employed asan insulator used in the pixel isolation portion 120. As the pixelisolation portion 120, a metal other than an insulator may be used toenhance the light shielding property, and voids may be included. Forexample, a thin insulator layer may be formed on the sidewall portion ofthe DTI structure and filled with metal. The pixel isolation portion 120can suppress transmission of incident light to adjacent pixels. That is,the crosstalk with adjacent pixels can be reduced by isolating one pixelfrom another pixel by using the pixel isolation portion 120.

On the light receiving surface side of the semiconductor layer 110, theinsulating layer 140 is provided for flattening the surface on whichlight enters. The insulating layer 140 is formed of a dielectricmaterial such as a silicon oxide film (SiO₂) or silicon nitride (Si₃N₄).A microlens 160 is formed on the surface of the insulating layer 140 onthe side where the light enters for collecting incident light to thepixel 10.

A wiring layer 190 included in the first wiring structure of FIG. 1 isformed on the second surface side of the first semiconductor region 111.The wiring layer 190 is formed of a conductor material havingcharacteristics of reflecting incident light transmitted through thelight receiving surface. The wiring layer 190 can function as areflecting layer for reflecting light incident from the light receivingsurface and emitted to the surface toward the semiconductor layer 110.The reflection of incident light in the semiconductor layer 110 can bepromoted and the efficiency of photoelectric conversion can be improvedby providing the wiring layer 190.

A pinning layer may be further provided between the light receivingsurface side of the semiconductor layer 110 on which the concavo-convexstructure 170 is formed and the insulating layer 140. The pinning layermay be formed by chemical vapor deposition or the like using a highdielectric material such as hafnium oxide (HfO₂), aluminum oxide (Al₂O₃)or silicon nitride (Si₃N₄). The pinning layer has a shape correspondingto the shape of the concavo-convex structure 170, and is preferablyformed sufficiently thin compared to the depth of the recess of theconcavo-convex structure 170. Forming the pinning layer allows tosuppress a dark current through defects existing on the light receivingsurface side of the semiconductor layer 110. The defects are, forexample, interface defects between the semiconductor layer 110 and theinsulating layer 140 provided thereon.

As shown in FIG. 6 , a light shielding portion 150 is provided betweenthe pixel isolation portion 120 and the insulating layer 140. Any knownmaterial having light shielding properties can be used for the lightshielding portion 150. The crosstalk with adjacent pixels can be furtherreduced by forming the light shielding portion 150.

In addition, a filter layer may be further provided between themicrolens 160 and the semiconductor layer 110. Various optical filterssuch as a color filter, an infrared light cut filter, and a monochromefilter can be used as the filter layer. As the color filter, an RGBcolor filter, an RGBW color filter, or the like can be used.

FIG. 7 is a cross-sectional view of the concavo-convex structure in thepresent embodiment. FIGS. 8A to 8C show plan views parallel to the lightreceiving surface in the lines A-A′, B-B′, and C-C′ of theconcavo-convex structure shown in FIG. 7 , respectively.

The concavo-convex structure 170 includes the trench 171 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 171includes an opening 171 a, a bottom 171 b, and an intermediate portion171 c. In the plan view of FIG. 8A, the opening 171 a is circular, and adiameter d1 of the opening 171 a is, for example, 0.2 μm or less, andpreferably 0.1 μm or less. In order to increase the diffraction ofincident light in the semiconductor layer 110, the diameter d1 of theopening 171 a is preferably smaller than the depth of the trench 171. Inthe plan view of FIGS. 8B and 8C, the intermediate portion 171 c of thetrench 171 forms an annular portion having a width w1. That is, theintermediate portion 171 c is defined by a sidewall 171 c 1 having adiameter d11 and a sidewall 171 c 2 having a diameter d12, and the widthw1 becomes (d12−d11)/2. Further, as the depth from the light receivingsurface to the intermediate portion 171 c increases, the diameter of theintermediate portion 171 c, that is, the diameters d11 and d12 increase.On the other hand, the width w1 can be constant regardless of the depthof the intermediate portion 171 c. In the cross-sectional view shown inFIG. 7 , the portion of the semiconductor layer 110 surrounded by thesidewalls 171 c 1 has a conical shape, and a conical top portion 110 ais disposed at a position deeper than the light receiving surface of thesemiconductor layer 110.

In the cross-sectional view shown in FIG. 7 , the trench 171 extendsobliquely from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110. The bottom 171 b facesthe opening 171 a. The angle α formed between the direction from theopening 171 a to the bottom 171 b of the trench 171 and the lightreceiving surface of the semiconductor layer 110 may be, for example,less than 90 degrees, but may be arbitrarily determined according to thematerial of the filling member described later and the wavelength of theincident light. The distance, or depth, from the light receiving surfaceof the semiconductor layer 110 to the bottom 171 b of the trench 171 maybe between 0.1 μm and 0.6 μm.

A filling member 1711 is formed in the trench 171. The filling member1711 includes a material having optical properties (for example, therefractive index) different from those of the semiconductor layer 110located around the trench 171, and can be a dielectric material such assilicon oxide film (SiO₂), silicon nitride (Si₃N₄), etc. In filling thefilling member 1711, the process used for forming the pixel isolationportion 120 can be used. The filling member 1711 does not necessarilyneed to be filled in the entire trench 171. For example, as shown inFIG. 9A, only a portion of the trench 171 may be provided with thefilling member 1711, and the other portion of the trench 171 may be avoid 1712. As shown in FIG. 9B, the entire inside of the trench 171 maybe the void 1712. Since the refractive index of the void 1712 is lowerthan that of the filling member 1711, the incident light passing throughthe void 1712 has a different optical path in the semiconductor layer110 from the incident light passing through the filling member 1711. Thedifference in the optical path of the incident light increases adifference in the refractive index in the trench 171, which increases aphase difference of the incident light. Thus, the diffraction effect ofthe incident light in the semiconductor layer 110 can be increased, andthe sensitivity to the incident light can be improved.

The trench 171 according to the present embodiment may be formed byperforming the anisotropic etching to the semiconductor layer 110.Specifically, the sensor substrate 1 including the semiconductor layer110 is attracted to a mounting table of an etching apparatus, and theanisotropic etching is performed with making the mounting tableinclined. The angle α can be adjusted by changing the inclination angleof the mounting table during etching. The mounting table is rotatedduring etching to form the trenches 171 as shown in FIGS. 7 and 8A to8C.

As described above, the trench 171 formed according to the presentembodiment extends obliquely from the light receiving surface of thesemiconductor layer 110 to the inside of the semiconductor layer 110.Therefore, the light incident on the semiconductor layer 110 can bescattered and refracted by the trench 171 multiple times. On the otherhand, assuming that the trench is formed perpendicular to the lightreceiving surface, the incident light is refracted only once. In thiscase, it is difficult to improve the absorption efficiency of incidentlight in the semiconductor layer 110 and to improve the sensitivity.According to the present embodiment, the trench 171 extends obliquelyfrom the light receiving surface of the semiconductor layer 110 to theinside of the semiconductor layer 110. Therefore, the light absorptionefficiency in the semiconductor layer 110 can be enhanced and thesensitivity can be improved, as the light incident on the semiconductorlayer 110 is scattered and refracted by the trench 171 multiple times.Such an effect becomes remarkable particularly for light having longwavelengths. Further, since the filling member 1711 havingcharacteristics different from those of the semiconductor layer 110 isdisposed in the trench, the effects of scattering and refraction becomegreater, which allows to further enhance the efficiency of thephotoelectric conversion.

Second Embodiment

FIG. 10 is a cross-sectional view of the concavo-convex structure of thesecond embodiment. In the first embodiment, the opening 171 a of thetrench 171 has a circular shape in plan view, but the shape of theopening 171 a is not limited to circular. For example, as shown in FIG.10 , the top portion 110 a of the semiconductor layer 110 may be exposedat the opening 171 a, and the opening 171 a may be formed in a circularshape. For example, the top portion 110 a of the semiconductor layer 110can be exposed in the opening 171 a by polishing the light receivingsurface of the semiconductor layer 110 of the first embodiment using thechemical mechanical polishing (CMP) or the like. Similarly to the firstembodiment, the present embodiment can also improve the sensitivity ofthe pixel 10 to incident light.

Third Embodiment

The third embodiment of the present disclosure will be described. In thefollowing embodiments, the configurations different from the first andsecond embodiments will be mainly described. FIG. 11 is across-sectional view of the concavo-convex structure of the presentembodiment. FIGS. 12A to 12C are plan views of the concavo-convexstructure of FIG. 11 taken along lines A-A′, B-B′, and C-C′,respectively.

The concavo-convex structure 170 includes a trench 172 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 172includes an opening 172 a, a bottom 172 b, and an intermediate portion172 c. A filling member 1721 is formed in the trench 172. In the planview of FIG. 12A, the opening 172 a is circular with a diameter d2. Inthe plan view of FIGS. 12B and 12C, the intermediate portion 172 c ofthe trench 172 constitutes an annular portion having a width w2. Thatis, the intermediate portion 172 c is defined by a sidewall 172 c 1having a diameter d21 and a sidewall 172 c 2 having a diameter d22, andthe width w2 is (d22−d21)/2. Further, as the depth from the lightreceiving surface to the intermediate portion 172 c increases, thediameter of the intermediate portion 172 c, that is, the diameters d21and d22 increase. The width w2 of the trench 172 in the plane at theC-C′ line shown in FIG. 12C is smaller than the width w2 of the trench172 in the plane at the B-B′ line. The width w2 becomes narrower as thedepth of the intermediate portion 172 c becomes deeper, and the bottom172 b of the trench 172 has a tapered shape in a cross-sectional view.

In the present embodiment, the trench 172 extends obliquely from thelight receiving surface of the semiconductor layer 110 to the inside ofthe semiconductor layer 110. Therefore, the light absorption efficiencyof the semiconductor layer 110 can be enhanced and the sensitivity canbe improved.

Fourth Embodiment

The fourth embodiment of the present disclosure will be described. FIG.13 is a cross-sectional view of the concavo-convex structure in thepresent embodiment. FIGS. 14A to 14C are plan views of theconcavo-convex structure of FIG. 13 taken along lines A-A′, B-B′, andC-C′, respectively.

The concavo-convex structure 170 includes a trench 173 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 173includes an opening 173 a, a bottom 173 b, and an intermediate portion173 c. A filling member 1731 is formed in the trench 173. In the planview of FIG. 14A, the opening 173 a is rectangular, and a width w3 ofthe opening 173 a is, for example, 0.2 μm or less, and preferably 0.1 μmor less. In the plan view of FIGS. 14B and 14C, the shape of theintermediate portion 173 c of the trench 173 corresponds to the shape ofthe opening 173 a and has a rectangular shape having the width w3. Theshape of the intermediate portion 173 c is constant regardless of thedepth of the intermediate portion 173 c. The shapes of the opening 173a, the intermediate portion 173 c, and the bottom 173 b in plan view maybe circular or polygonal other than rectangular.

Also in the present embodiment, the trench 173 extends obliquely fromthe light receiving surface of the semiconductor layer 110 to the insideof the semiconductor layer 110. Thus, the light absorption efficiency inthe semiconductor layer 110 can be enhanced to improve the sensitivity.

Fifth Embodiment

A fifth embodiment of the present disclosure will be described. FIG. 15is a cross-sectional view of the concavo-convex structure of the presentembodiment. FIGS. 16A to 16C are plan views of the concavo-convexstructure of FIG. 15 taken along lines A-A′, B-B′, and C-C′,respectively.

The concavo-convex structure 170 includes a trench 174 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 174includes an opening 174 a, a bottom 174 b, and an intermediate portion174 c. A filling member 1741 is formed in the trench 174. In the planview of FIG. 16A, the opening 174 a has a rectangular shape having awidth w4. In a plan view of FIGS. 16B and 16C, the two intermediateportions 174 c branch from the one opening 174 a and extend inside thesemiconductor layer 110. That is, the two intermediate portions 174 cshare the one opening 174 a. The shape of the intermediate portion 174 ccorresponds to the opening 174 a, and the intermediate portion 174 c hasa rectangular shape having the width w4 as in the opening 174 a. Theshape of the intermediate portion 174 c is constant regardless of thedepth of the intermediate portion 174 c. On the other hand, the twointermediate portions 174 c are separated from each other as the twointermediate portions 174 c extend deep from the light receivingsurface.

Also in the present embodiment, the trench 174 extends obliquely fromthe light receiving surface of the semiconductor layer 110 to the insideof the semiconductor layer 110. Thus, the light absorption efficiency inthe semiconductor layer 110 can be enhanced and the sensitivity can beimproved.

Sixth Embodiment

The sixth embodiment of the present disclosure will be described. FIG.17 is a cross-sectional view of the concavo-convex structure of thepresent embodiment. FIGS. 18A to 18C are plan views of theconcavo-convex structure of FIG. 17 taken along lines A-A′, B-B′, andC-C′, respectively.

The concavo-convex structure 170 includes a trench 175 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 175includes an opening 175 a, a bottom 175 b, and an intermediate portion175 c. A filling member 1751 is formed in the trench 175. In the presentembodiment, unlike the fifth embodiment, the four intermediate portions175 c share the one opening 175 a. The shape of the intermediate portion175 c corresponds to the shape of the opening 175 a and has arectangular shape having a width w5. The shape of the intermediateportion 175 c is constant regardless of the depth of the intermediateportion 175 c. On the other hand, the four intermediate portions 175 care separated from each other as the four intermediate portions 175 cextend deep from the light receiving surface.

Also in the present embodiment, the trench 175 extends obliquely fromthe light receiving surface of the semiconductor layer 110 to the insideof the semiconductor layer 110. Thus, the light absorption efficiency inthe semiconductor layer 110 can be enhanced and the sensitivity can beimproved. The number of intermediate portions 175 c is not limited tofour, and more intermediate portions 175 c may share the one opening 175a.

Seventh Embodiment

The trenches according to the first to the sixth embodiments describedabove can be arranged in any pattern on the light receiving surface ofthe semiconductor layer 110 including the APD 11. For example, as shownin FIG. 19A, the plurality of trenches 171 including the openings 171 aaccording to the first embodiment can be arranged at equal intervals inthe row and column directions of the light receiving surface of thesemiconductor layer 110 in plan view. Also, as shown in FIG. 19B, theplurality of trenches 171 may be arranged in a staggered manner in therow or column direction to have a houndstooth shape in plan view. Thepatterns of trenches 171 may be different for each pixel. For example,as shown in FIG. 19C, the plurality of trenches 171 may be arrangedaccording to the pattern of FIG. 19A in one of the two pixels separatedby the pixel isolation portion 120, and the plurality of trenches 171may be arranged according to the pattern of FIG. 19B in the other of thetwo pixels. The trenches do not necessarily have to be arranged in aregular pattern, but may be arranged randomly.

Eighth Embodiment

The eighth embodiment of the present disclosure will be described. FIG.20 is a cross-sectional view of the concavo-convex structure of thepresent embodiment. FIGS. 21A to 21C are plan views of theconcavo-convex structure of FIG. 20 taken along lines A-A′, B-B′, andC-C′, respectively.

The concavo-convex structure 170 includes a trench 176 obliquelyextending from the light receiving surface of the semiconductor layer110 to the inside of the semiconductor layer 110, and the trench 176includes an opening 176 a, a bottom 176 b, and an intermediate portion176 c. A filling member 1761 is formed in the trench 176. In the planview of FIG. 21A, the opening 176 a has an elongated shape having widthsw61 and w62. The width w61 is, for example, 0.2 μm or less, andpreferably 0.1 μm or less. The width w62 of the opening 176 a is largerthan the width w61 and may correspond to, for example, the width of apixel. In the plan view of FIGS. 21B and 21C, the shape of theintermediate portion 176 c of the trench 176 corresponds to the shape ofthe opening 176 a and has the widths w61 and w62. The shape of theintermediate portion 176 c is constant regardless of the depth of theintermediate portion 176 c. The shape of the opening 176 a may be anellipse or a polygon other than a rectangle.

The trenches according to the present embodiment may be arranged in anypattern on the light receiving surface of the semiconductor layer 110.For example, as shown in FIG. 22A, the multiple trenches 176 can bearranged in the column direction of the light receiving surface of thesemiconductor layer 110 in plan view. Further, for example, as shown inFIG. 22B, the multiple trenches 176 can be arranged in a grid shape inthe row and column directions of the light receiving surface of thesemiconductor layer 110 in a plan view.

Ninth Embodiment

The ninth embodiment of the present disclosure will be described. Thetrenches shown in the above embodiments may be arranged in a differentpattern for each pixel. FIG. 23 is a cross-sectional view of theconcavo-convex structure of the present embodiment. Each of pixels 10A,10B and 10C has the semiconductor layer 110 and the insulating layer140. The pixel isolation portion 120 is formed between the pixels 10A,10B and 10C. The light shielding portion 150 is formed between the pixelisolation portion 120 and the insulating layer 140.

The light receiving surfaces of the pixels 10A, 10B, and 10C are formedwith trenches 177A, 177B, and 177C according to the present disclosure,respectively. The trenches 177A, 177B, and 177C have trench lengths L1,L2, and L3, respectively, in a cross-sectional view. The trench lengthL2 is greater than the trench length L1, and the trench length L3 isgreater than the trench lengths L1, L2. By changing the depth to whichthe trenches are formed for each pixel as described in the presentembodiment, the light absorption efficiency can be optimized for eachpixel according to the wavelength band of incident light and thematerial of the member filled in the trenches 177A, 177B and 177C.

Tenth Embodiment

The tenth embodiment according to the present disclosure will bedescribed. FIG. 24 is a cross-sectional view of the concavo-convexstructure of the present embodiment. Each of pixels 10A, 10B and 10C hasthe semiconductor layer 110 and the insulating layer 140. The pixelisolation portion 120 is formed between the pixels 10A, and 10C. Thelight shielding portion 150 is formed between the pixel isolationportion 120 and the insulating layer 140.

The light receiving surfaces of the pixels 10A, 10B, and 10C are formedwith trenches 178A, 178B, and 178C according to the present disclosure,respectively. The trenches 178A, 178B, and 178C extend to form anglesα1, α2, and α3 with the light receiving surface of the semiconductorlayer 110, respectively. The angle α2 is greater than the angle α1, andthe angle α3 is greater than the angles α1, α2. By changing the anglebetween the trench and the light receiving surface for each pixel asdescribed in the present embodiment, the light absorption efficiency canbe optimized for each pixel according to the wavelength band of incidentlight and the material of the member filled in the trenches 178A, 178Band 178C.

Eleventh Embodiment

The eleventh embodiment of the present disclosure will be described.FIG. is a cross-sectional view of the concavo-convex structure of thepresent embodiment. Each of the pixels 10A, 10B and 10C has thesemiconductor layer 110 and the insulating layer 140. The pixelisolation portion 120 is formed between the pixels 10A, 10B and 10C. Thelight shielding portion 150 is formed between the pixel isolationportion 120 and the insulating layer 140.

The light receiving surfaces of the pixels 10A, 10B, and 10C are formedwith trenches 179 according to the present disclosure. The pixel 10Cincludes more trenches 179 than the pixels 10A, 10B. Further, the pixel10A includes more trenches 179 than the pixel 10B. By changing thenumber of trenches to be formed for each pixel as described in thepresent embodiment, the light absorption efficiency can be optimized foreach pixel according to the wavelength band of incident light and thematerial of the member to be filled in the trench 179.

In the example shown in FIG. 25 , the trenches 179 are formed on thelight receiving surfaces of the pixels 10A, 10B, and 10C. As shown inFIG. 26 , for example, however, the trenches 179 may be formed only onthe surface of the first surface side of the semiconductor layer 110 ofthe pixel 10A. In the example shown in FIG. 26 , the pixel can be apixel for detecting light with a long wavelength band having arelatively low light absorption efficiency.

Twelfth Embodiment

In the above embodiments, the trenches are formed in the semiconductorlayer 110. However, the trenches do not necessarily have to be formed inthe semiconductor layer 110. FIG. 27 is a cross-sectional view ofmultiple adjacent pixels in the present embodiment. As shown in FIG. 27, the pixel 10 includes the semiconductor layer 110 and the insulatinglayer 140. A concavo-convex structure 180 including trenches 181 isformed on the surface of the insulating layer 140 on the side wherelight enters. The shape of the trench 181, the member to be filled inthe trench 181, the optical characteristics and the like may be similarto any of the trenches 171 to 179 described above. The configurationaccording to the present embodiment also allows to enhance theabsorption efficiency of incident light and improve the sensitivity.

Thirteenth Embodiment

An imaging system according to the thirteenth embodiment of the presentdisclosure will be described with reference to FIG. 28 . FIG. 28 is ablock diagram of a photodetection system according to the presentembodiment. The photodetection system according to the presentembodiment is an imaging system that acquires an image based on incidentlight. The photoelectric conversion device in the above-describedembodiments can be applied to various imaging systems. Examples of theimaging system include a digital still camera, a digital camcorder, acamera head, a copier, a fax machine, a cellular phone, an in-vehiclecamera, an observation satellite, and a surveillance camera. FIG. 28 isa block diagram of a digital still camera as an example of an imagingsystem.

An imaging system 7 illustrated in FIG. 28 includes a barrier 706, alens 702, an aperture 704, an imaging device 70, a signal processingunit 708, a timing generation unit 720, a general control/operation unit718, a memory unit 710, a storage medium control I/F unit 716, a storagemedium 714, and an external I/F unit 712. The barrier 706 protects thelens, and the lens 702 forms an optical image of an object on theimaging device 70. The aperture 704 varies the amount of light passingthrough the lens 702. The imaging device 70 is configured like thephotoelectric conversion device of the above embodiments, and convertsan optical image formed by the lens 702 into image data. The signalprocessing unit 708 performs a process such as compression and variouscorrections of data on the imaging data output from the imaging device70.

The timing generation unit 720 outputs various timing signals to theimaging device 70 and the signal processing unit 708. The generalcontrol/operation unit 718 controls the overall digital still camera,and the memory unit 710 temporarily stores image data. The storagemedium control I/F unit 716 is an interface for recording or readingimage data in or from the storage medium 714, and the storage medium 714is a removable storage medium such as a semiconductor memory forrecording or reading image data. The external I/F unit 712 is aninterface for communicating with an external computer or the like. Thetiming signal or the like may be input from the outside of the imagingsystem 7, and the imaging system 7 may include at least the imagingdevice 70 and the signal processing unit 708 that processes the imagesignal output from the imaging device 70.

In the present embodiment, the imaging device 70 and the signalprocessing unit 708 are formed on different semiconductor substrates.However, the imaging device and the signal processing unit 708 may beformed on the same semiconductor substrate.

Each pixel of the imaging device 70 may include a first photoelectricconversion unit and a second photoelectric conversion unit. The signalprocessing unit 708 may process the pixel signal based on the chargegenerated in the first photoelectric conversion unit and the pixelsignal based on the charge generated in the second photoelectricconversion unit, and acquire the distance information from the imagingdevice 70 to the object.

Fourteenth Embodiment

FIG. 29 is a block diagram of a photodetection system according to thepresent embodiment. More specifically, FIG. 29 is a block diagram of aranging image sensor using the photoelectric conversion device accordingto the above-described embodiments.

As illustrated in FIG. 29 , a ranging image sensor 401 includes anoptical system 402, a photoelectric conversion device 403, an imageprocessing circuit 404, a monitor 405, and a memory 406. The rangingimage sensor 401 receives light (modulated light, pulsed light) emittedfrom a light source device 411 toward an object and reflected by thesurface of the object. The ranging image sensor 401 can acquire adistance image corresponding to the distance to the object based on thetime from light emission to light reception.

The optical system 402 includes one or a plurality of lenses, guidesimage light (incident light) from the object to the photoelectricconversion device 403, and forms an image on a light receiving surface(sensor portion) of the photoelectric conversion device 403.

As the photoelectric conversion device 403, the photoelectric conversiondevice of each of the above embodiments can be applied. Thephotoelectric conversion device 403 supplies a distance signalindicating a distance obtained from the received light signal to theimage processing circuit 404.

The image processing circuit 404 performs image processing for forming adistance image based on the distance signal supplied from thephotoelectric conversion device 403. The distance image (image data)obtained by image processing can be displayed on the monitor 405 andstored (recorded) in the memory 406.

By applying the photoelectric conversion device described above to theranging image sensor 401 configured as described above, a more accuratedistance image can be acquired.

Fifteenth Embodiment

The technology according to the present disclosure can be applied tovarious products. For example, techniques according to the presentdisclosure may be applied to endoscope surgery systems which is anexample of the photodetection system.

FIG. 30 is a schematic view of an endoscope surgery system according tothe present embodiment. FIG. 30 shows a state in which an operator(physician) 1131 performs surgery on a patient 1132 on a patient bed1133 using an endoscope surgery system 1103. As shown, the endoscopesurgery system 1103 includes an endoscope 1100, a surgery tool 1110, anda cart 1134 on which various devices for endoscopic surgery are mounted.

The endoscope 1100 includes a lens barrel 1101 in which an area of apredetermined length from the distal end is inserted into the bodycavity of the patient 1132, a camera head 1102 connected to the proximalend of the lens barrel 1101, and an arm 1121. Although FIG. 30illustrates the endoscope 1100 configured as a so-called rigid scopehaving the rigid lens barrel 1101, the endoscope 1100 may be configuredas a so-called flexible scope having a flexible lens barrel.

An opening into which an objective lens is fitted is provided at adistal end of the lens barrel 1101. A light source device 1203 isconnected to the endoscope 1100. Light generated by the light sourcedevice 1203 is guided to the distal end of the barrel by a light guideextended inside the lens barrel 1101, and is irradiated toward anobservation target in the body cavity of the patient 1132 via anobjective lens. The endoscope 1100 may be a straight-viewing scope anoblique-viewing scope, or a side-viewing scope.

An optical system and a photoelectric conversion device are providedinside the camera head 1102, and reflected light (observation light)from an observation target is focused on the photoelectric conversiondevice by the optical system. The observation light is photoelectricallyconverted by the photoelectric conversion device, and an electric signalcorresponding to the observation light, that is, an image signalcorresponding to the observation image is generated. As thephotoelectric conversion device, the photoelectric conversion devicedescribed in each of the above embodiments can be used. The image signalis transmitted to a camera control unit (CCU) 1135 as RAW data.

The CCU 1135 includes a central processing unit (CPU), a graphicsprocessing unit (GPU), and the like, and controls overall operations ofthe endoscope 1100 and a display device 1136. Further, the CCU 1135receives an image signal from the camera head 1102, and performs variouskinds of image processing for displaying an image based on the imagesignal, such as development processing (demosaic processing).

The display device 1136 displays an image based on the image signalsubjected to the image processing by the CCU 1135 under the control ofthe CCU 1135.

The light source device 1203 includes, for example, a light source suchas a light emitting diode (LED), and supplies irradiation light to theendoscope 1100 when capturing an image of an operating part or the like.

An input device 1137 is an input interface to the endoscope surgerysystem 1103. The user can input various types of information and inputinstructions to the endoscope surgery system 1103 via the input device1137.

A treatment tool controller 1138 controls the actuation of an energytreatment tool 1112 for ablation of tissue, incision, sealing of bloodvessels, etc.

The light source device 1203 is capable of supplying irradiation lightto the endoscope 1100 when capturing an image of the surgical site, andmay be, for example, a white light source formed by an LED, a laserlight source, or a combination thereof. When a white light source isconfigured by a combination of RGB laser light sources, the outputintensity and output timing of each color (each wavelength) can becontrolled with high accuracy. Therefore, the white balance of thecaptured image can be adjusted in the light source device 1203. In thiscase, laser light from each of the RGB laser light sources may beirradiated onto the observation target in a time-division manner, anddriving of the image pickup device of the camera head 1102 may becontrolled in synchronization with the irradiation timing. Thus, imagescorresponding to R, G, and B can be captured in a time-division manner.According to this method, a color image can be obtained withoutproviding a color filter in the image pickup device.

The driving of the light source device 1203 may be controlled such thatthe intensity of light output from the light source device 1203 ischanged at predetermined time intervals. By controlling the driving ofthe image pickup device of the camera head 1102 in synchronization withthe timing of changing the intensity of light to acquire an image in atime-division manner, and by synthesizing the images, it is possible togenerate an image in a high dynamic range without so-called blackout andwhiteout.

Further, the light source device 1203 may be configured to be able tosupply light in a predetermined wavelength band corresponding to speciallight observation. In special light observation, for example, thewavelength dependence of light absorption in body tissue can be used.Specifically, a predetermined tissue such as a blood vessel in thesurface layer of the mucosa is imaged with high contrast by irradiatinglight in a narrow band compared to the irradiation light (i.e., whitelight) during normal observation. Alternatively, in special lightobservation, fluorescence observation for obtaining an image byfluorescence generated by irradiation with excitation light may beperformed. In the fluorescence observation, excitation light can beirradiated to the body tissue to observe fluorescence from the bodytissue, or a reagent such as indocyanine green (ICG) can be locallyinjected into the body tissue and the body tissue can be irradiated withexcitation light corresponding to the fluorescence wavelength of thereagent to obtain a fluorescence image. The light source device 1203 maybe configured to be able to supply narrowband light and/or excitationlight corresponding to such special light observation.

Sixteenth Embodiment

A light detection system and A movable body of the present embodimentwill be described with reference to FIGS. 31, 32A, 32B, and 32C. In thepresent embodiment, an example of an in-vehicle camera is illustrated asa light detection system.

FIG. 31 is a schematic diagram of a light detection system according tothe present embodiment, and illustrates an example of a vehicle systemand a light detection system mounted on the vehicle system. A lightdetection system 1301 includes photoelectric conversion devices 1302,image pre-processing units 1315, an integrated circuit 1303, and opticalsystems 1314. The optical system 1314 forms an optical image of anobject on the photoelectric conversion device 1302. The photoelectricconversion device 1302 converts the optical image of the object formedby the optical system 1314 into an electric signal. The photoelectricconversion device 1302 is the photoelectric conversion device of any oneof the above-described embodiments. The image pre-processing unit 1315performs predetermined signal processing on the signal output from thephotoelectric conversion device 1302. The function of the imagepre-processing unit 1315 may be incorporated in the photoelectricconversion device 1302. The light detection system 1301 is provided withat least two sets of the optical system 1314, the photoelectricconversion device 1302, and the image pre-processing unit 1315, and anoutput signal from the image pre-processing units 1315 of each set isinput to the integrated circuit 1303.

The integrated circuit 1303 is an integrated circuit for use in animaging system, and includes an image processing unit 1304 including astorage medium 1305, an optical ranging unit 1306, a parallaxcalculation unit 1307, an object recognition unit 1308, and anabnormality detection unit 1309. The image processing unit 1304 performsimage processing such as development processing and defect correction onthe output signal of the image pre-processing unit 1315. The storagemedium 1305 performs primary storage of captured images and storesdefect positions of image capturing pixels. The optical ranging unit1306 focuses or measures the object. The parallax calculation unit 1307calculates distance measurement information from the plurality of imagedata acquired by the plurality of photoelectric conversion devices 1302.The object recognition unit 1308 recognizes an object such as a car, aroad, a sign, or a person. When the abnormality detection unit 1309detects the abnormality of the photoelectric conversion device 1302, theabnormality detection unit 1309 issues an abnormality to a main controlunit 1313.

The integrated circuit 1303 may be realized by dedicated hardware, asoftware module, or a combination thereof. It may be realized by a fieldprogrammable gate array (FPGA), an application specific integratedcircuit (ASIC), or the like, or may be realized by a combination ofthese.

The main control unit 1313 (movable body controller) controls overalloperations of the light detection system 1301, a vehicle sensor 1310, acontrol unit 1320, and the like. Without the main control unit 1313, thelight detection system 1301, the vehicle sensor 1310, and the controlunit 1320 may individually have a communication interface, and each ofthem may transmit and receive control signals via a communicationnetwork, for example, according to the CAN standard.

The integrated circuit 1303 has a function of transmitting a controlsignal or a setting value to the photoelectric conversion device 1302 byreceiving a control signal from the main control unit 1313 or by its owncontrol unit.

The light detection system 1301 is connected to the vehicle sensor 1310,and can detect a traveling state of the host vehicle such as a vehiclespeed, a yaw rate, a steering angle, and the like, an environmentoutside the host vehicle, and states of other vehicles and obstacles.The vehicle sensor 1310 is also a distance information acquisition unitthat acquires distance information to the object. The light detectionsystem 1301 is connected to a driving support control unit 1311 thatperforms various driving support functions such as an automatic steeringfunction, an automatic cruise function, and a collision preventionfunction. In particular, with regard to the collision determinationfunction, based on detection results of the light detection system 1301and the vehicle sensor 1310, it is determined whether or not there is apossibility or occurrence of collision with another vehicle or anobstacle. Thus, avoidance control is performed when a possibility ofcollision is estimated and a safety device is activated when collisionoccurs.

The light detection system 1301 is also connected to an alert device1312 that issues an alarm to a driver based on a determination result ofthe collision determination unit. For example, when the possibility ofcollision is high as the determination result of the collisiondetermination unit, the main control unit 1313 performs vehicle controlsuch as braking, returning an accelerator, suppressing engine output, orthe like, thereby avoiding collision or reducing damage. The alertdevice 1312 issues a warning to a user using means such as an alarm of asound or the like, a display of alarm information on a display unitscreen such as a car navigation system and a meter panel, and avibration application to a seatbelt and a steering wheel.

The light detection system 1301 according to the present embodiment cancapture an image around the vehicle, for example, the front or the rear.FIGS. 32A, 32B, and 32C are schematic diagrams of a movable bodyaccording to the present embodiment, and illustrate a configuration inwhich an image of the front of the vehicle is captured by the lightdetection system 1301.

The two photoelectric conversion devices 1302 are arranged in front of avehicle 1300. Specifically, it is preferable that a center line withrespect to a forward/backward direction or an outer shape (for example,a vehicle width) of the vehicle 1300 be regarded as a symmetry axis, andthe two photoelectric conversion devices 1302 be arranged in linesymmetry with respect to the symmetry axis. This makes it possible toeffectively acquire distance information between the vehicle 1300 andthe object to be imaged and determine the possibility of collision.Further, it is preferable that the photoelectric conversion device 1302be arranged at a position where it does not obstruct the field of viewof the driver when the driver sees a situation outside the vehicle 1300from the driver's seat. The alert device 1312 is preferably arranged ata position that is easy to enter the field of view of the driver.

Next, a failure detection operation of the photoelectric conversiondevice 1302 in the light detection system 1301 will be described withreference to FIG. 33 . FIG. 33 is a flowchart illustrating an operationof the light detection system according to the present embodiment. Thefailure detection operation of the photoelectric conversion device 1302may be performed according to steps S1410 to S1480 illustrated in FIG.33 .

In step S1410, the setting at the time of startup of the photoelectricconversion device 1302 is performed. That is, setting information forthe operation of the photoelectric conversion device 1302 is transmittedfrom the outside of the light detection system 1301 (for example, themain control unit 1313) or the inside of the light detection system1301, and the photoelectric conversion device 1302 starts an imagingoperation and a failure detection operation.

Next, in step S1420, the photoelectric conversion device 1302 acquirespixel signals from the effective pixels. In step S1430, thephotoelectric conversion device 1302 acquires an output value from afailure detection pixel provided for failure detection. The failuredetection pixel includes a photoelectric conversion element in the samemanner as the effective pixel. A predetermined voltage is written to thephotoelectric conversion element. The failure detection pixel outputs asignal corresponding to the voltage written in the photoelectricconversion element. Steps S1420 and S1430 may be executed in reverseorder.

Next, in step S1440, the light detection system 1301 performs adetermination of correspondence between the expected output value of thefailure detection pixel and the actual output value from the failuredetection pixel. If it is determined in step S1440 that the expectedoutput value matches the actual output value, the light detection system1301 proceeds with the process to step S1450, determines that theimaging operation is normally performed, and proceeds with the processto step S1460. In step S1460, the light detection system 1301 transmitsthe pixel signals of the scanning row to the storage medium 1305 andtemporarily stores them. Thereafter, the process of the light detectionsystem 1301 returns to step S1420 to continue the failure detectionoperation. On the other hand, as a result of the determination in stepS1440, if the expected output value does not match the actual outputvalue, the light detection system 1301 proceeds with the process to stepS1470. In step S1470, the light detection system 1301 determines thatthere is an abnormality in the imaging operation, and issues an alert tothe main control unit 1313 or the alert device 1312. The alert device1312 causes the display unit to display that an abnormality has beendetected. Then, in step S1480, the light detection system 1301 stops thephotoelectric conversion device 1302 and ends the operation of the lightdetection system 1301.

Although the present embodiment exemplifies the example in which theflowchart is looped for each row, the flowchart may be looped for eachplurality of rows, or the failure detection operation may be performedfor each frame. The alert of step S1470 may be notified to the outsideof the vehicle via a wireless network.

Further, in the present embodiment, the control in which the vehicledoes not collide with another vehicle has been described, but thepresent embodiment is also applicable to a control in which the vehicleis automatically driven following another vehicle, a control in whichthe vehicle is automatically driven so as not to protrude from the lane,and the like. Further, the light detection system 1301 can be appliednot only to a vehicle such as a host vehicle, but also to a movable body(movable apparatus) such as a ship, an aircraft, or an industrial robot.In addition, the present embodiment can be applied not only to a movablebody but also to an apparatus utilizing object recognition such as anintelligent transport systems (ITS). The photoelectric conversion deviceof the present disclosure may be a configuration capable of furtheracquiring various types of information such as distance information.

Seventeenth Embodiment

FIG. 34A is a diagram illustrating a specific example of an electronicdevice according to the present embodiment, and illustrates glasses 1600(smart glasses). The glasses 1600 are provided with a photoelectricconversion device 1602 described in the above embodiments. That is, theglasses 1600 are an example of a light detection system to which thephotoelectric conversion device 1602 described in each of the aboveembodiments can be applied. A display device including a light emittingdevice such as an OLED or an LED may be provided on the back surfaceside of a lens 1601. One photoelectric conversion device 1602 or theplurality of photoelectric conversion devices 1602 may be provided.Further, a plurality of types of photoelectric conversion devices may becombined. The arrangement position of the photoelectric conversiondevice 1602 is not limited to that illustrated in FIG. 34A.

The glasses 1600 further comprise a control device 1603. The controldevice 1603 functions as a power source for supplying power to thephotoelectric conversion device 1602 and the above-described displaydevice. The control device 1603 controls operations of the photoelectricconversion device 1602 and the display device. The lens 1601 is providedwith an optical system for collecting light to the photoelectricconversion device 1602.

FIG. 34B illustrates glasses 1610 (smart glasses) according to oneapplication. The glasses 1610 include a control device 1612, and aphotoelectric conversion device corresponding to the photoelectricconversion device 1602 and a display device are mounted on the controldevice 1612. A lens 1611 is provided with a photoelectric conversiondevice in the control device 1612 and an optical system for projectinglight emitted from a display device, and an image is projected on thelens 1611. The control device 1612 functions as a power source forsupplying power to the photoelectric conversion device and the displaydevice, and controls operations of the photoelectric conversion deviceand the display device. The control device 1612 may include aline-of-sight detection unit that detects the line of sight of thewearer. Infrared radiation may be used to detect the line of sight. Theinfrared light emitting unit emits infrared light to the eyeball of theuser who is watching the display image. The reflected light of theemitted infrared light from the eyeball is detected by an imaging unithaving a light receiving element, whereby a captured image of theeyeball is obtained. A reduction unit that reduces light from theinfrared light emitting unit to the display unit in a plan view may beemployed and the reduction unit reduces a degradation in image quality.

The control device 1612 detects the line of sight of the user withrespect to the display image from the captured image of the eyeballobtained by imaging the infrared light. Any known method can be appliedto the line-of-sight detection using the captured image of the eyeball.As an example, a line-of-sight detection method based on a Purkinjeimage due to reflection of irradiation light at a cornea can be used.

More specifically, a line-of-sight detection process based on a pupilcornea reflection method is performed. By using the pupil corneareflection method, a line-of-sight vector representing a direction(rotation angle) of the eyeball is calculated based on the image of thepupil included in the captured image of the eyeball and the Purkinjeimage, whereby the line-of-sight of the user is detected.

The display device of the present embodiment may include a photoelectricconversion device having a light receiving element, and may control adisplay image of the display device based on line-of-sight informationof the user from the photoelectric conversion device.

Specifically, the display device determines a first view field regiongazed by the user and a second view field region other than the firstview field region based on the line-of-sight information. The first viewfield region and the second view field region may be determined by acontrol device of the display device, or may be determined by anexternal control device. In the display area of the display device, thedisplay resolution of the first view field region may be controlled tobe higher than the display resolution of the second view field region.That is, the resolution of the second view field region may be lowerthan that of the first view field region.

The display area may include a first display region and a second displayregion different from the first display region. A region having a highpriority may be determined from the first display region and the seconddisplay region based on the line-of-sight information. The first viewfield region and the second view field region may be determined by acontrol device of the display device, or may be determined by anexternal control device. The resolution of the high priority area may becontrolled to be higher than the resolution of the region other than thehigh priority region. That is, the resolution of a region having arelatively low priority can be reduced.

It should be noted that an artificial intelligence (AI) may be used indetermining the first view field region and the region with highpriority. The AI may be a model configured to estimate an angle of aline of sight and a distance to a target on the line-of-sight from animage of an eyeball, and the AI may be trained using training dataincluding images of an eyeball and an angle at which the eyeball in theimages actually gazes. The AI program may be provided in either adisplay device or a photoelectric conversion device, or may be providedin an external device. When the external device has the AI program, theAI program may be transmitted from a server or the like to a displaydevice via communication.

When the display control is performed based on the line-of-sightdetection, the present embodiment can be preferably applied to a smartglasses which further includes a photoelectric conversion device forcapturing an image of the outside. The smart glasses can displaycaptured external information in real time.

OTHER EMBODIMENTS

The present disclosure is not limited to the above embodiment, andvarious modifications are possible. For example, an example in whichsome of the configurations of any of the embodiments are added to otherembodiments or an example in which some of the configurations of any ofthe embodiments are replaced with some of the configurations of otherembodiments is also an embodiment of the present disclosure.

Embodiment(s) of the present disclosure can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present disclosure has been described with reference toexemplary embodiments, it is to be understood that the disclosure is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2022-092372, filed on Jun. 7, 2022, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A photoelectric conversion device comprising: apixel isolation portion arranged between adjacent pixels in a pluralityof pixels formed in a semiconductor layer; and a concavo-convexstructure formed on a light receiving surface of the semiconductorlayer, wherein the concavo-convex structure includes a trench extendingtoward an oblique direction from the light receiving surface to aninside of the semiconductor layer, and wherein the trench is filled withmaterial that is different from material of the semiconductor layerpositioned around the trench.
 2. A photoelectric conversion devicecomprising: a pixel isolation portion arranged between adjacent pixelsin a plurality of pixels formed in a semiconductor layer; and aconcavo-convex structure formed on a light receiving surface of thesemiconductor layer, wherein the concavo-convex structure includes atrench extending toward an oblique direction from the light receivingsurface to an inside of the semiconductor layer, and wherein the trenchis filled with material that has a refractive index different from arefractive index of the semiconductor layer positioned around thetrench.
 3. The photoelectric conversion device according to claim 1,wherein the trench includes an annular portion having a circular shapein a cross section parallel to the light receiving surface, and whereina diameter of the annular portion becomes greater with depth from thelight receiving surface.
 4. The photoelectric conversion deviceaccording to claim 3, wherein a width of the annular portion is constantregardless of depths from the light receiving surface to the annularportion.
 5. The photoelectric conversion device according to claim 3,wherein a width of the annular portion becomes narrower with depth fromthe light receiving surface to the annular portion.
 6. The photoelectricconversion device according to claim 1, wherein the trench includes anopening having a circular shape in a plan view of the light receivingsurface.
 7. The photoelectric conversion device according to claim 6,wherein the multiple openings are arranged in: row and column directionsin parallel in the plan view of the light receiving surface; or a rowdirection or a column direction with a houndstooth shape in a staggeredmanner in the plan view of the light receiving surface.
 8. Thephotoelectric conversion device according to claim 1, wherein the trenchincludes: an opening on the light receiving surface; a bottom facing theopening; and an intermediate portion between the opening and the bottom,wherein the intermediate portion has a shape corresponding to a shape ofthe opening.
 9. The photoelectric conversion device according to claim8, wherein the opening has a rectangular or circular shape in a planview of the light receiving surface.
 10. The photoelectric conversiondevice according to claim 8, wherein the openings are arranged in alatticework form in a plan view of the light receiving surface.
 11. Thephotoelectric conversion device according to claim 8, wherein thetrenches share the opening.
 12. The photoelectric conversion deviceaccording to claim 8, wherein the intermediate portions separate fartherfrom each other with depth of the light receiving surface.
 13. Thephotoelectric conversion device according to claim 8, wherein theopenings are arranged in: row and column directions in parallel in aplan view of the light receiving surface; or a row direction or a columndirection with a houndstooth shape in a staggered manner in a plan viewof the light receiving surface.
 14. The photoelectric conversion deviceaccording to claim 1, wherein the trench is formed in the semiconductorlayer.
 15. The photoelectric conversion device according to claim 1,wherein the trench is formed in an insulating layer of the semiconductorlayer.
 16. The photoelectric conversion device according to claim 1,wherein the trench is partially filled to include a void.
 17. Thephotoelectric conversion device according to claim 1, wherein thephotoelectric conversion device is a back-illuminated type.
 18. Thephotoelectric conversion device according to claim 1, wherein thephotoelectric conversion device is a single-photon avalanche diode(SPAD) type.
 19. An imaging system comprising: an imaging deviceincluding the photoelectric conversion device according to claim 1; anda signal processing circuit configured to process imaging data outputfrom the imaging device.
 20. A movable body comprising: thephotoelectric conversion device according to claim 1; a distanceinformation acquisition circuit configured to acquire distanceinformation to an object from a signal output from the photoelectricconversion device; and a control circuit configured to control themovable body based on the distance information.